"‎We've made enough progress in the last days to merit staying until Wednesday. There are several difficult issues still remaining,"‎ State Department spokeswoman Marie Harf said.

White House press secretary Josh Earnest said the talks in Lausanne would continue another day as "long as the conversations continue to be productive."

Diplomats and negotiators were still working as an initial deadline approached, but more time appeared necessary to reach a framework deal.

How long talks will continue was unclear. French Foreign Minister Laurent Fabius informed the Iranians that he will return to Paris at dawn Wednesday in an apparent effort to force the Iranians' hand, Western diplomatic sources told CNN.

Hamid Ba'idinejad from Iran's Foreign Ministry said earlier Tuesday there are no "artificial" deadlines and a deal will be reached, when each issue has been resolved.

Diplomats told CNN that there has been progress, but gaps remain.

For Iran, that means there's a light at the end of the tunnel for crippling sanctions. For the West, it means real hope that it's possible to loosen up on Tehran while still being confident that it won't develop nuclear weapons.

The international sanctions relief issue has been resolved, according to Ba'idinejad. "We have had long discussions on this, but there are issues that are related to sanctions that are still under consideration," Ba'idinejad said. He added that is not the only issue that needs to be worked out Tuesday night or Wednesday.

The thing is, nuclear physics is complicated. So are the international dynamics anytime you're talking about Iran and the West, with mutual distrust and contempt a shared sentiment for years.

That's why it's taken so long to even get to this point, and why what's happening in Lausanne matters. Before you can iron out nitty-gritty technical details in a permanent, comprehensive pact -- which carries the more important deadline of June 30 -- you have to agree on what you're going to talk about.

Final accord deadline in three months

What happens if Wednesday passes and there's no framework agreement? In the short term, it appears, not much.

The real deadline isn't for three months, after all. As for the March 31 date, there's nothing to stop the parties from continuing to talk -- though an Iranian official told state-run Press TV that no one had raised the idea of an extension as of late Monday.

"All emphasize that the chance should not be missed, and they are all doing their best," Ba'idinejad said.

Russian minister: 'Chances are high' for a deal

So far, there's been a lot of meetings, with occasional smiles for cameras followed by foreign ministers talking behind closed doors.

After working through the previous night, representatives from the key players -- most of them foreign ministers -- met all day Tuesday to try to resolve differences in what Chinese Foreign Minister Wang Yi described as "the final stage" of "these marathon-like negotiations."

The parties are either on the verge of a milestone agreement or still separated on some crucial points, depending on who you listen to.

Russian Foreign Minister Sergey Lavrov is among the optimists. Russia has been closer than most to Iran even as it's gone along with sanctions.

"Prospects for this round of talks are not bad, I would even say good," Lavrov said before heading to Switzerland for the final round of negotiations, according to state-run Sputnik news agency. "The chances are high."

But in comments Monday to CNN, a more cautious Kerry conceded there was "a little more light there today, but there are still some tricky issues."

"There still remain some difficult issues," the top U.S. diplomat said. "We are working very hard to work those through ... with a view to get something done."

Three sticking points

Iran has been under intense international pressure and has faced crippling sanctions over its nuclear program for years.

The sides began moving away from stalemate with Iranians' 2013 election of President Hassan Rouhani, who has insisted that Iran wants a peaceful nuclear energy program but not weapons. Viewed as a moderate -- especially compared with other powerful figures in Iran, including the country's Supreme Leader Ayatollah Ali Khamenei -- Rouhani campaigned on a platform that he'd work to help Iran's economy by reducing its rifts with the outside world.

His government has had some success easing those tensions, spearheading interim agreements that have loosened some sanctions. But a comprehensive and final deal has remained elusive.

There's been discussion on what to do with Iran's existing fissile material -- which is important because, as long as it's still around, that will make it easier to produce a nuclear weapon more quickly. Still, U.S. officials suggested Monday the debate over this has been overblown, with Harf calling it one outstanding issue though "it hasn't, quite honestly, been one of the toughest ones."

More important are three points that have dominated the talks in Lausanne:

• How quickly or slowly Iran will be allowed to advance its nuclear technology in the last five years of the 15-year agreement.

• How quickly the crushing U.N. sanctions will go away.

• Whether sanctions will snap back into place if Iran violates the deal.

Iran wants them gone for good. Lavrov claims that the U.N. Security Council will lift the sanctions right away, but other international negotiators want to merely suspend them, so they can be reapplied as leverage if Iran does not keep its end of the bargain.

Agreement on those points is crucial, a Western diplomat said.

"There cannot be an agreement if we do not have answers to these questions," the diplomat said.

Stockpile controversy

Another point of contention: what to do with the nuclear substances Iran already has.

Diplomats had told journalists about a plan for Iran to ship its fissile material to Russia. The idea is that if Tehran doesn't have a nuclear stockpile at its fingertips, it will have a longer "breakout time" to make a nuclear weapon should negotiations fall apart.

Iran isn't ready to do that, one of its negotiators said Sunday.

"The export of stocks of enriched uranium is not in our program," Iranian Deputy Foreign Minister Abbas Araghchi said, "and we do not intend to send them abroad."

But on Monday, U.S. officials said the rumblings in the media about the stockpile issue were overblown.

Negotiators had not yet decided any specifics about the disposal of fissile material, and Iran has made the comments many times before, a senior State Department official said, citing a list of previous examples of such statements in press reports.

Obstacles remain, even with a framework pact

With or without a deal, a lot can change in the next three months. For one, the devil is in the details -- any one of which could throw everyone back to square one.

Then there's the possibility that a deal ironed out in Switzerland is rejected by any of the key players.

That's been raised as a possibility in the United States, even though a Washington Post-ABC News Poll conducted in the past few days found that 59% of respondents support a deal in Iran that would restrict its nuclear program in exchange for the lifting of sanctions.

Earlier this month, 47 Republican senators wrote directly to the Iranian government, reminding it that any deal it reaches with U.S. President Barack Obama might be moot once his term ends in less than two years.

One person leading the charge against a possible deal, even though he'll have no direct part in shaping it, is Israeli Prime Minister Benjamin Netanyahu.

Reiterating points he made earlier this month to the U.S. Congress, Netanyahu said Tuesday "the greatest threat to our security and safety and our future is Iranians' attempt to become nuclear."

"And the agreement that is being formed in Lausanne," the Israeli leader said, "is paving the road to that result."

French magazine Paris Match and German newspaper Bild reported that a video recovered from a cell phone at the wreckage site showed the inside of the plane moments before it crashed.

"One can hear cries of 'My God' in several languages. Metallic banging can also be heard more than three times, perhaps of the pilot trying to open the cockpit door with a heavy object. Towards the end, after a heavy shake, stronger than the others, the screaming intensifies. Then nothing," Paris Match reports.

The two publications described the video, which they said was found by a source close to the investigation, but did not post it on their websites.

Lt. Col. Jean-Marc Menichini, a French Gendarmerie spokesman in charge of communications on rescue efforts around the Germanwings crash site, told CNN that the reports were "completely wrong" and "unwarranted." Cell phones have been collected at the site, he said, but that they "hadn't been exploited yet."

Menichini said he believed the cell phones would need to be sent to the Criminal Research Institute in Rosny sous Bois, near Paris, in order to be analyzed by specialized technicians working hand-in-hand with investigators. But none of the cellphones found so far have been sent to the institute, Menichini said.

Asked whether rescue staff could have leaked a memory card to the media, Menichini answered with a categorical "no".

Airline: Co-pilot reported depression

Lufthansa, meanwhile, announced that co-pilot Andreas Lubitz told his Lufthansa flight training school in 2009 that he had a "previous episode of severe depression."

The airline is sharing that information and documents -- including training and medical records -- with public prosecutors.

Authorities have said Lubitz purposely crashed Flight 9525 into the French Alps on March 24, killing all 150 people aboard.

His girlfriend knew he had psychological issues but "did not know the extent of the problems," a European government official briefed on the investigation into last week's crash told CNN on Tuesday.

The girlfriend told investigators the couple were working through the issues together and "were optimistic" they could solve the problems; she was just as surprised as everyone else by what he did to the plane, the source says.

The girlfriend also told investigators Lubitz had seen an eye doctor and a neuropsychologist, both of whom deemed him unfit to work recently and concluded he had psychological issues, according to the source.

Lubitz complained about vision problems; the eye doctor diagnosed a psychosomatic disorder and gave him an "unfit for work" note, the source said.

Investigators are looking into whether Lubitz feared his medical condition would cause him to lose his pilot's license, the source said, adding that while flying was "a big part of his life," it's only one theory being considered.

Another source, a law enforcement official briefed on the investigation, told CNN that authorities believe the primary motive for Lubitz to bring down the plane was that he feared he would not be allowed to fly because of his medical problems.

Too stressed?

Lubitz told the neuropsychologist that he was too stressed with work, the European government official briefed on the investigation said.

The official said he was not aware of any suicidal tendencies reported by Lubitz to the doctors, but that investigators believe he was suicidal.

Airline officials have said that if Lubitz went to a doctor on his own, he would have been required to self-report if deemed unfit to fly.

The European government official also reiterated that German media tabloid reports that the girlfriend is pregnant or had major personal problems are all speculation and rumor.

The girlfriend and the co-pilot had not, as was widely reported by some media, broken up the day before the crash, the source said.

Official: Lubitz had suicidal tendencies

Earlier, a spokesman for the prosecutor's office in Dusseldorf said Lubitz suffered from suicidal tendencies at some point before his aviation career.

Investigators have not found any writings or conversations where Lubitz shared his motives or confessed to any plans, prosecutor's spokesman Christoph Kumpa said. However, medical records reveal that Lubitz was suicidal at one time and underwent psychotherapy. This was before he ever got his pilot's license, Kumpa said.

Kumpa emphasized there's no evidence suggesting Lubitz was suicidal or acting aggressively before the crash.

The prosecutor's office confirmed what some media outlets had reported about doctors deeming Lubitz unfit to fly, though there were no physical illnesses found.

Recovery efforts continue

While investigators search for clues to Lubitz's motivation, recovery workers continue the grim task of searching for the remains of those killed in the March 24 crash.

Menichini, the Gendarmerie spokesman, told CNN that a new path has been completed linking Le Vernet, a nearby community, to the mountainous ravine where the plane's debris is scattered.

It will be used by rescue teams to access the area, he said.

Capt. Yves Naffrechoux, also of the Gendarmerie unit, said Monday that the 1-kilometer path would cut down on the time it takes to reach the crash site considerably.

The trip will now take 30 minutes from Seyne-les-Alps, the staging post for the operation, with less walking involved and thus less fatigue, but also with fewer risks than helicopter transfers.

Two helicopters are still working in case weather conditions improve and allow them to fly, Menichini said.

The remains of at least 78 people on board the plane have been identified so far using DNA analysis.

Naffrechoux warned Monday that "it may not be possible to find the human remains of all the 150 passengers, as some of them may have been pulverized by the crash."

But French President Francois Hollande, speaking alongside German Chancellor Angela Merkel in Berlin, was more positive, saying that it should be possible to identify all the victims by the end of the week.

A simple stone memorial has been set up at Le Vernet, where grieving relatives of those killed have laid flowers and held prayers.

The opening of the road, which must still be paved, will eventually allow family members also to reach the spot where their loved ones died.

Authorities say there are some 26 families of six different nationalities in the area Tuesday.

However, Patricia Willaert, head of the Alpes de Haute-Provence district, told reporters that Lubitz's family was not among those to have come since the crash.

"There had been some rumors, but they have not come to the site," she said. "The family of the co-pilot has not come. We have no knowledge of information informing us of that."

Willaert said some 450 people close to the victims had already traveled to the area, with more expected to come during the Easter weekend.

"The priority has been to welcome them in the best possible way," she said. She praised the mobilization of local citizens, who spontaneously offered 2,000 beds to accommodate the victims' families.

German investigators and French criminal investigators are due to work together at the crash site Wednesday, Dusseldorf police said.

Medical record emerging

Much attention has focused on Lubitz's state of mind, with suggestions that he may have had mental health issues.

Lubitz, 27, passed his annual pilot recertification medical examination in summer 2014, a German aviation source told CNN. He had started working as a commercial pilot in 2013, said Lufthansa, the parent company of Germanwings.

An official with Lufthansa said that the exam only tests physical health, not psychological health.

It's unknown whether Lubitz mentioned his problems on a form that asks yes-or-no questions about physical and mental illness, suicide attempts and medications. European pilots must fill out the form to be recertified.

Federal aviation authorities, not the airline, issue the form. The form is privileged information, and Lufthansa never sees a pilot's completed form, an airline representative said.

The airline would only get a "clear to fly" notice from the aviation doctors alerting the airline that a pilot has completed recertification.

Safety investigation

France's accident investigation agency, the BEA, said Tuesday that the ongoing safety investigation was focusing on a more detailed analysis of the flight history leading up to the crash, based on the audio recovered from the cockpit voice recorder and any other available data.

BEA spokeswoman Martine Del Bono told CNN: "A deliberate act by a man with a disturbed psychological profile is a possible scenario. The first step of the investigation is to describe more precisely what happened."

This will be based mainly on analysis of the cockpit voice recorder, to be supplemented by data from the flight data recorder if it is found, she said.

"But we will also look at other events with possibly similar scenarios, try to understand if there are systemic weaknesses which may contribute or facilitate such scenarios.

"We will in particular look at the cockpit door locking as well as the criteria and procedures applied to detect specific psychological profiles."

Lufthansa said in a statement Tuesday that it was canceling its 60th anniversary celebrations, planned for April 15.

Instead, the company will provide a live broadcast for its employees of an official state ceremony to be held April 17 in Cologne Cathedral for bereaved families and friends to remember the victims, it said.

Ronnie Buckner, 61, told police he was eating salsa with Phyllis Jefferson, 50, at his apartment Sunday when Jefferson said he was eating all of it, reports The Associated Press.

Buckner said Jefferson became angry and stabbed him in the leg with a pen, reports the AP. He said Jefferson knocked over a television while she was grabbing a knife with which she stabbed him again, reports Gawker.com.

According to a police report, Jefferson said she stabbed Buckner because "she wanted to leave."

Jefferson was arrested and charged with felonious assault and misdemeanor criminal endangering, reports the AP.

Leave it to Google to make April Fools' Day into throwback fun by combining Google Maps with Pac-Man.

The massive tech company is known for its impish April Fools' Day pranks, and Google Maps has been at the center of a few, including a Pokemon Challenge and a treasure map. This year the company was a day early to the party, rolling out the Pac-Man game Tuesday.

It's easy to play: Simply pull up Google Maps on your desktop browser, click on the Pac-Man icon on the lower left, and your map suddenly becomes a Pac-Man course.

Twitterers have been tickled by the possibilities, playing Pac-Man in Manhattan, on the University of Illinois quad, in central London and down crooked Lombard Street in San Francisco, among many locations.

Google says the game is also playable on mobile devices in certain cities. But don't wait, because the company says the game "will only be around for a little while."

Who cares about rush hour? When those dark red lines of expressways and thoroughfares can be festooned with Pac-Man dots, it's a good reason to stay late at work.

Although your computer mouse is no substitute for a good old arcade joystick.